feat: Implement virtual hosting for multi-domain Gemini server

- Add hostname-based request routing for multiple capsules per server
- Parse virtual host configs from TOML sections ([hostname])
- Implement per-host certificate and content isolation
- Add comprehensive virtual host testing and validation
- Update docs and examples for multi-host deployments

This enables Pollux to serve multiple Gemini domains from one instance,
providing the foundation for multi-tenant Gemini hosting.

examples/development.toml

@@ -0,0 +1,30 @@
+# Pollux Development Configuration
+#
+# Example configuration for local development with self-signed certificates.
+# NOT suitable for production use.
+
+bind_host = "127.0.0.1"
+port = 1965
+log_level = "debug"
+max_concurrent_requests = 100
+
+# Local development site
+["localhost"]
+root = "./content"
+cert = "./tmp/cert.pem"
+key = "./tmp/key.pem"
+
+# Alternative hostname for testing
+["gemini.local"]
+root = "./content"
+cert = "./tmp/cert.pem"
+key = "./tmp/key.pem"
+
+# Generate self-signed certificates with:
+# mkdir -p tmp
+# openssl req -x509 -newkey rsa:2048 \
+#   -keyout tmp/key.pem \
+#   -out tmp/cert.pem \
+#   -days 365 \
+#   -nodes \
+#   -subj "/CN=localhost"

examples/single-host.toml

@@ -0,0 +1,16 @@
+# Pollux Single Host Example Configuration
+#
+# Example configuration for a single Gemini capsule.
+# For multiple hosts, use virtual hosting instead.
+
+# Global settings
+bind_host = "127.0.0.1"
+port = 1965
+log_level = "info"
+max_concurrent_requests = 100
+
+# Host configuration
+["example.com"]
+root = "./content"
+cert = "./tmp/cert.pem"
+key = "./tmp/key.pem"

examples/virtual-hosting.toml

@@ -0,0 +1,35 @@
+# Pollux Virtual Hosting Example Configuration
+#
+# This example shows how to configure multiple Gemini capsules
+# on a single server instance.
+
+# Global settings (applied to all hosts unless overridden)
+bind_host = "0.0.0.0"
+port = 1965
+log_level = "info"
+max_concurrent_requests = 1000
+
+# Main website
+["example.com"]
+root = "/var/gemini/example.com"
+cert = "/etc/ssl/example.com.crt"
+key = "/etc/ssl/example.com.key"
+
+# Blog subdomain
+["blog.example.com"]
+root = "/var/gemini/blog"
+cert = "/etc/ssl/blog.example.com.crt"
+key = "/etc/ssl/blog.example.com.key"
+
+# Personal site
+["tilde.example.com"]
+root = "/home/user/public_gemini"
+cert = "/etc/ssl/tilde.crt"
+key = "/etc/ssl/tilde.key"
+
+# Development site (different port)
+["dev.example.com"]
+root = "/home/dev/gemini"
+cert = "/etc/ssl/dev.crt"
+key = "/etc/ssl/dev.key"
+port = 1966